A pizzeria mistakenly sold pizza laced with THC. Here’s how it happened.

A pizza shop in Wisconsin shocked patrons when it apologized for inadvertently selling pizzas containing THC, the primary psychoactive component in cannabis. They figured it out when customers reported feeling odd after eating slices of their pie.

“This is incredibly serious to us and we can’t imagine anything worse than betraying the faith that our customers have in us to provide a product made with utmost care and concern,” Famous Yeti’s Pizza co-owner Cale Ryan said in a statement posted to Facebook on Oct. 25. “If we lost your faith in us and we never get to serve you again, I completely understand.”

Here’s what we know about the incident, and why eating THC in pizza may cause stronger psychoactive effects than consuming cannabis in some other ways.

Dough used in about 70 orders was prepared with THC-contaminated oil

Oil containing THC was in a storage space in the cooperative commercial kitchen that the shop shares with other vendors, according to a statement on Famous Yeti’s website. Ryan told The Washington Post he knew there was a vendor in the space who made THC-infused brownies, but when reports of unexplained reactions to the food started coming in, his mind didn’t jump to THC. Recreational cannabis use is not legal in Wisconsin.

Ryan initially thought some of the vegetable toppings, possibly the spinach, had been contaminated or gone bad. The fire department even checked the building, located in Stoughton, Wisconsin, for a carbon monoxide leak, concerned that some patrons’ symptoms were consistent with CO exposure.

Eating THC in pizza and other fatty foods makes the effects stronger, experts say

Eating cannabis raw is unlikely to get you high, said Darin Erickson, the associate director of research at the University of Minnesota’s Cannabis Research Center, because the compounds in it are activated during cooking or smoking. People who make edibles infuse cannabis into some kind of fat — in this case, oil — and then use that fat to make other kinds of food.

The high you get from weed that’s eaten instead of smoked can also be different, Erickson said, because cannabis is metabolized differently in the gut. The timing is different, too. Smokers and vapers feel the effects of cannabis within 5 to 10 minutes, while it can take around an hour for those who use edibles. It can be even faster if someone is eating high-fat foods.

Fats increase the absorption of cannabinoids, based on preclinical research in rats, said Tory Spindle, an associate professor of psychiatry and behavioral sciences at Johns Hopkins University School of Medicine.

“This increased absorption means that a person would feel stronger effects than if the THC was suspended in something that was not fatty,” he said.

It is the reverse of the relationship between eating and drinking alcohol.

“The interactions between food and cannabis is actually the opposite of food and alcohol,” Spindle said. “Which many people don’t realize.”